This study is a continuation of research into the biochemistry of synovium in joints subjected to acute trauma. Experimental dislocation, ligament instability, and intra-articular fractures are produced in the knees of rabbits, and the synovium studied at serial intervals from trauma induction. Biochemical studies focus on the role of lysosomal enzymes and the degradative activity of the synovium toward cartilage. An in vitro system has been devised to measure the actual degradation of the proteoglycan moiety of labelled cartilage by the synovium under study in a tissue culture incubation system. This activity is correlated with quantitative determination of lysosomal enzymes, and with the histology and histochemistry of the affected synovium. These data will be compared with similar data obtained from the synovium of matched groups of animals subjected to standard intra-articular insults to produce degenerative and inflammatory arthritis. An ultimate goal of these studies is to identify a biochemically measurable point in the progression of traumatic arthritis beyond which irreversible changes in cartilage occur, and prior to which cartilage destruction can be reversed.